OG详解-OG1 数学1 Q7

The correct answer is 30. The value of f (x) when  x = 4 can be found by substituting 4 for x in the given equation f(x) = 7x+2. This yields f (4) =7 (4) + 2, or f(4) = 30 . Therefore, when  x = 4, the value of f (x) is 30.